Formulations and methods for providing progestin-only contraception while minimizing adverse side effects associated therewith

ABSTRACT

Formulations and methods for providing progestin-only contraception to a woman while minimizing various side effects, such as breakthrough bleeding, that are normally associated with progestin-only contraception are disclosed and described. In one aspect, the method can include transdermally administering a formulation having a contraceptively effective amount of a single progestin as the sole active hormonal agent to the woman as part of a contraceptive regimen.

This application is a continuation of U.S. patent application Ser. No.11/205,297 filed on Aug. 15, 2005.

FIELD OF THE INVENTION

The present invention relates to formulations and methods for effectivecontraception while minimizing or reducing adverse side effectsassociated with progestin-only contraception, such as breakthroughbleeding. Accordingly, this invention involves the fields ofpharmaceutical sciences, medicine, chemistry and other health sciences.

BACKGROUND OF THE INVENTION

Progesterone is a primary progestational substance produced by ovariancells of the corpus luteum. Progestins, e.g., progesterone and itsderivatives, transform the proliferative endometrium into secretoryendometrium. This change in the endometrium is essential to theimplantation of a fertilized ovum and the development of a placentaduring conception and the early stages of pregnancy. Many of thesechanges require, however, the presence of estrogen. Therefore, in theabsence of estrogen, progestins can exert an atrophic effect on theendometrium, as well as various other contraceptive effects. Suchcontraceptive effects may vary depending on the concentration and thenature of the particular progestin involved.

Accordingly, various progestins have been utilized as contraceptivedrugs due to their convenient nature coupled with their fairlypredictable ovulatory and progestational effects. One specific progestinthat has received much attention is norethindrone (NE) and its prodrugnorethindrone acetate (NEA). Both compounds have been orally andtransdermally administered as part of a number of specific formulations.Though the actions of these and other progestins can vary, many exerteffects on the ovaries, the endometrium, and the cervix. For example,certain long acting injectable progestins in appropriate doses can causeendometrial atrophy. Oral preparations can vary according to the drugand the dose. Some permitting a normal endometrium and others causingregression. Progestins can also inhibit ovulation by suppressing theovarian response to gonadotropins. This may cause a failure to ovulateor, if ovulation does occur, a smaller hyposecreting corpus luteum.Particularly high doses of progestins tend to suppress the pituitaryrelease of lutenizing hormone and the hypothalamic release ofgonadotropin releasing hormone (GnRH), which can act to preventovulation through decreased gonadotropin output. Progestins also tend toincrease the viscosity of cervical mucous secretions and thereforeimpede the mobility of sperm. These and other actions of progestins canact in combination to provide effective contraception.

One undesirable issue with the use of oral progestin-only contraceptionis the need for consistent dosing at the same time each day. The onsetof cervical mucus thickening typically occurs within about 2 hours ofdosing and lasts for about 16 to 19 hours. By about 24 hours post dose,the cervical mucus returns to substantially normal viscosity. Sincethickening of cervical mucus is such an important factor in attainingthe progestin-induced contraceptive effect, it is extremely importantthat dosing take place substantially 24 hours apart in order to maintainthe elevated mucus viscosity. Of course, such a stringent dosing regimenis inconvenient and runs a high risk of non-compliance.

Additionally, progestin-only contraception tends to induce certainadverse side effects. One of the most inconvenient of such side effectsis spotting and breakthrough bleeding. Such bleeding can beunpredictable or irregular in onset, and in some cases bleeding can bemore Voluminous than in regular menstruation. Such effects can oftenweigh heavily against the supposed convenience of this form of birthcontrol.

Therefore, formulations and methods for progestin-only contraceptionwhich minimize the incidence of adverse side effects, particularlyspotting and breakthrough bleeding, continue to be sought.

SUMMARY OF THE INVENTION

Accordingly, the present invention discloses methods of providingeffective progestin-only contraception to a woman while minimizingadverse side effects that are normally associated with progestin-onlycontraception. Such adverse side effects include, without limitation,strokes, myocardial infarctions, embolisms, breakthrough bleeding, etc.In one aspect, such a method can include transdermally administering aformulation having a contraceptively effective amount of a singleprogestin as the sole active hormonal agent to the woman.

A variety of progestins may be used as the active agent in theformulations and methods of the present invention. Specific examples ofprogestins may include without limitation, progesterone,hydroxyprogesterone, megestrol acetate, dimethisterone, norgestrel,levonorgestrel, medroxyprogesterone acetate, desogestrel, norgestimate,ethynodiol diacetate, norethindrone, norethindrone acetate, andnorethynodrel, including their active metabolites and derivatives. Inone specific aspect, the progestin can be or consist of progesterone. Inanother aspect, the progestin can include or consist of norethindrone.In another aspect, the progestin can include or consist of norethindroneacetate. In yet another aspect, the progestin can include or consist ofnorethynodrel.

The formulations of the present invention may include various dosages ofprogestins to achieve a therapeutic effect. For example, in one aspectthe progestin may be either norethindrone or norethindrone acetateadministered at a rate and an amount that provides a minimumnorethindrone serum level of at least about 160 pg/ml in order to causeand sustain physiologic events in the woman resulting in contraception,while at the same time providing a maximum norethindrone serum level ofless than about 2400 pg/ml in order to avoid a significant incidence ofadverse side effects. In another aspect, the maximum norethindrone serumlevel may be from about 240 pg/ml to about 1920 pg/ml. In yet anotheraspect, the maximum norethindrone serum level may be from about 300pg/ml to about 1200 pg/ml. In a further aspect, the maximumnorethindrone serum level can be from about 400 pg/ml to about 1100pg/ml. In one aspect, the minimum norethindrone serum level can be atleast about 300 pg/ml. In yet another aspect, the minimum norethindroneserum level can be at least about 350 pg/ml.

Various physiologic events resulting from the administration of aprogestin are believed to contribute to contraception. Such physiologicevents may include, without limitation, suppression of ovulation, athickening of cervical mucus, and combinations thereof. Contraceptivephysiologic events can be sustained for varying amounts of timefollowing the initial administration, depending on the dosage form, thenature of any penetration enhancer present, the amount of progestin inthe formulation, etc. In one aspect, physiologic events may be sustainedfor a period of up to at least 168 hours. In another aspect, physiologicevents associated with contraception may be sustained for a period fromabout 24 hours to about 168 hours. In yet another aspect, contraceptionmay be sustained for a period of from about 24 hours to about 96 hours.In a further aspect, contraception may be sustained for a period of fromabout 48 hours to about 168 hours.

As such, either norethindrone or norethindrone acetate may also beadministered at a rate and an amount that provides a minimumnorethindrone serum level sufficient to cause and sustain contraceptionfor a period of from about 24 hours to about 168 hours and which avoidsa significant incidence of adverse side effects by attaining a maximumnorethindrone serum level that is less than about 2400 pg/ml.

In addition to the progestin, the transdermal formulations of thepresent invention may optionally include various additional additives ofa non-hormonal nature. For example, delivery of the progestin may beimproved by utilizing one or more permeation enhancers. As such, theformulations can include a permeation enhancer. In one aspect, thepermeation enhancer can include, or consist of a sorbitan ester-typeenhancer. One example of a sorbitan ester-type enhancer is, withoutlimitation, sorbitan monooleate. In another aspect, the permeationenhancer can include a lauryl-type enhancer. Examples of lauryl typeenhancers may include, without limitation, lauryl alcohol,1-lauryl-2-pyrrolidone, and mixtures thereof. In yet another aspect, thepermeation enhancer may include a combination of lauryl alcohol anisopropyl myristate. In a further aspect, the permeation enhancer mayinclude a polyol-type enhancer, such as dipropylene glycerol. While theamount of penetration enhancer used may vary depending on a number ofcriteria, such as the type of enhancer selected, the material of thecarrier, etc., in one aspect, the enhancer amount may be from about0.01% w/w to about 50% w/w of the transdermal composition. In anotheraspect, the enhancer amount may be from about 3% w/w to about 15% w/w ofthe transdermal composition.

In one specific aspect of the present invention, a method of providingprogestin-only contraception to a woman while minimizing adverse sideeffects associated with progestin-only contraception is provided. Themethod may include transdermally administering a formulation havingnorethindrone acetate as the sole active hormonal ingredient in anamount of from about 5% w/w to about 25% w/w of the transdermalformulation and a permeation enhancer in an amount from about 0.01% w/wto about 50% w/w of the transdermal formulation. The formulation may beadministered at a rate and an amount that provides a minimumnorethindrone serum level of at least 200 pg/ml in order to cause andsustain physiologic events in the woman resulting in contraception for aperiod of from about 24 to about 168 hours, and also provide a maximumnorethindrone serum level of less than about 2400 pg/ml in order toavoid a significant incidence of adverse side effects. The maximumnorethindrone serum level may be obtained from about 24 to about 96hours following administration.

In another aspect of the present invention, a method of providingprogestin-only contraception to a woman while minimizing adverse sideeffects associated with the progestin-only contraception is provided.The method may include transdermally administering a formulation havingeither norethindrone or norethindrone acetate as the sole activehormonal agent to the woman, at a rate and an amount that provides aminimum norethindrone serum level sufficient to cause and sustaincontraception for a period of from about 24 to about 168 hours and whichmaintains a maximum norethindrone serum level that may be up to about 15times greater than the minimum norethindrone serum level. In yet anotheraspect, the maximum norethindrone serum level may be up to about 8 timesgreater than the minimum norethindrone serum level. In a further aspect,the maximum norethindrone serum level may be up to about 4 times greaterthan the minimum norethindrone serum level. In yet another aspect, themaximum norethindrone serum level may be up to about 2.75 times greaterthan the minimum norethindrone serum level.

The present invention additionally encompasses various kits,formulations, and articles of manufacture to be used in providingprogestin-only contraception to a woman while minimizing adverse sideeffects, such as breakthrough bleeding, associated with progestin-onlycontraception. In one aspect, such a kit may include a transdermallyadministrable formulation including norethindrone acetate as the soleactive agent in an amount of from about 5% w/w to about 25% w/w of thetransdermal formulation and a permeation enhancer in an amount of fromabout 0.01% w/w to about 50% w/w of the transdermal formulation. Theformulation may be administered at a rate and an amount that provides aminimum norethindrone serum level of at least 160 pg/ml in order tocause and sustain physiologic events in the woman resulting incontraception for a period of from about 24 hours to about 168 hours,and also may provide a maximum norethindrone serum level of less thanabout 2400 pg/ml, which is obtained from about 24 to about 96 hoursfollowing administration, in order to avoid a significant incidence ofadverse side effects. The kit may also include a set of instructionsdescribing a method of using the transdermally administrableformulation.

Numerous transdermal dosage forms are contemplated for use with thepresent invention. For example, in one aspect the kit can contain aformulation having a dosage form selected from the group consisting oftransdermal patches, ointments, lotions, gels, pastes, mousses,aerosols, creams, gels, and combinations thereof. In one aspect, theformulation may be in a transdermal patch dosage form, and the kit mayinclude at least three patches to be administered for up to about 168hours. The kit may also contain a placebo patch.

There has thus been outlined, rather broadly, the more importantfeatures of the invention so that the detailed description thereof thatfollows may be better understood, and so that the present contributionto the art may be better appreciated. Other features of the presentinvention will become clearer from the following detailed description ofthe invention, taken with the accompanying claims, or may be learned bythe practice of the invention.

DETAILED DESCRIPTION

A. Definitions

In describing and claiming the present invention, the followingterminology will be used in accordance with the definitions set forthbelow.

The singular forms “a,” “an,” and, “the” include plural referents unlessthe context clearly dictates otherwise. Thus, for example, reference to“an adhesive” includes reference to one or more of such adhesives, andreference to “an excipient” includes reference to one or more of suchexcipients.

The terms “progestin” or “progestogen” refer to any natural or syntheticprogestational substance that mimics some or all of the actions ofprogesterone. “Progestin” and “progestogen” may also refer to anynatural or synthetic substance that exerts a biological orpharmacological action primarily by binding to progestin receptors.Examples include, but are not limited to, progesterone,medroxyprogesterone acetate, hydroxyprogesterone, megestrol acetate,dimethisterone, norgestrel, levonorgestrel, desogestrel, norgestimate,ethynodiol diacetate, norethynodrel, norethindrone, and norethindroneacetate, esters, derivatives, prodrugs, active metabolites, and isomersthereof. Progestins have been administered to women in order to provideeffective contraception. While the amount of a progestin required toachieve this effect vary from woman to woman, methods for determiningappropriate or effective amounts for the purpose of contraception arewell known to those of ordinary skill in the art. Progestins themselvesare well known in the art, a partial description of which can be foundon pgs. 1386-1388 of Remington: The Science and Practice of Pharmacy(20^(th) ed. 2000), which is incorporated herein by reference.

As used herein in, “norethindrone,” or “NE” refers to a compound havingthe general chemical structure:

Norethindrone is well known in the art, and is listed as monograph 6790on pg. 1149 of the Merck Index (12^(th) ed. 1996), which is incorporatedherein by reference.

As used herein, “norethindrone acetate,” or “NEA” refers to a compoundhaving the general chemical structure:

Norethindrone acetate is well known in the art as an ester type prodrugof norethindrone and is described on pg. 1096 of Remington: The Scienceand Practice of Pharmacy (19″ ed. 1995), which is incorporated herein byreference.

The terms “breakthrough bleeding” and “intermenstral bleeding” can beused interchangeably, and are defined as any vaginal bleeding occurringduring the menstrual cycle of a woman on hormonal contraceptives,excluding contiguous bleeding with menses. Breakthrough bleeding caninclude any discernable vaginal bleeding, including spotting.

As used herein, “subject” refers to a mammal that may benefit from theadministration of a drug composition or method of this invention.Examples of subjects include humans, especially females, and may alsoinclude other animals such as horses, pigs, cattle, dogs, cats, rabbits,and aquatic mammals.

As used herein, the terms “formulation” and “composition” are usedinterchangeably and refer to a mixture of two or more compounds,elements, or molecules. In some aspects the terms “formulation” and“composition” may be used to refer to a mixture of an active agent witha carrier or other excipients. The terms “drug,” “pharmaceutical,”“active agent,” and “bioactive agent” are also used interchangeably torefer to a pharmacologically active substance or composition. Theseterms of art are well-known in the pharmaceutical and medicinal arts.

As used herein, “transdermal refers to the route of administration takenby a drug that is applied to and absorbed through an area of skin. Insome aspects, the skin may be substantially unbroken. Thus the terms“transdermal formulation” and “transdermal composition” can be usedinterchangeably, and refer to formulations or compositions that areapplied to a surface of the skin and transdermally absorbed. Examples oftransdermal formulations include but are not limited to, ointments,creams, gels, transdermal patches, sprays, lotions, mousses, aerosols,nasal delivery systems, pulmonary delivery systems, buccal andsublingual delivery systems, vaginal rings, and pastes. The term“transdermal administration” thus refers to the transdermal applicationof a formulation or composition. Transdermal administration can beaccomplished by applying, pasting, rolling, attaching, pouring,pressing, rubbing, spraying, etc., of a transdermal preparation orformulation onto a skin surface. These and additional methods ofadministration are well known in the art.

The terms “transdermal delivery system,” “transdermal patches” or simply“patches” refer to a matrix or liquid reservoir type of transdermaldelivery device which is used to transdermally deliver defined doses ofa substance, over a specific application period.

By the term “matrix”, “matrix system”, or “matrix patch” is meant acomposition comprising an effective amount of a drug dissolved ordispersed in a polymeric phase, often a pressure sensitive adhesive,which may also contain other ingredients, such as a permeationenhancers, skin irritation reducing agents, excipients, plasticizers,emollients, and other optional ingredients. This definition is meant toinclude embodiments wherein such polymeric phase is laminated to apressure sensitive adhesive or used within an overlay adhesive.

One example of a transdermal patch for administering a progestin inaccordance with this invention is a matrix-type patch which comprises anocclusive backing that is impermeable to the progestin and defines theface or top surface of the patch and a solid or semisolid matrix layercomprised of a homogeneous blend of the hormone, a polymeric pressuresensitive adhesive carrier, and optionally one or more skin permeationenhancers. Matrix patches are known in the art of transdermal drugdelivery. Examples without limitation, of adhesive matrix transdermalpatches are those described or referred to in U.S. Pat. Nos. 5,985,317,5,783,208, 5,626,866, 5,227,169, 5,122,383, and 5,460,820 which areincorporated by reference in their entirety.

Another example of a transdermal patch for administering a progestin inaccordance with this invention is a liquid reservoir system (LRS) typepatch which comprises progestin and other optional ingredients, such asa permeation enhancer, in a carrier vehicle. The carrier vehiclecomprises a fluid of desired viscosity, such as a gel or ointment, whichis formulated for confinement in a reservoir having an impermeablebacking and a skin contacting permeable membrane, or membrane adhesivelaminate providing diffusional contact between the reservoir contentsand the skin. For application, a peelable release liner is removed andthe patch is attached to the skin surface. LRS patches are known in theart of transdermal drug delivery. Examples without limitation, of LRStransdermal patches are those described or referred to in U.S. Pat. Nos.4,849,224, 4,983,395, which are incorporated by reference in theirentirety.

The terms “skin,” “skin surface,” “derma,” “epidermis,” and similarterms are used interchangeably herein, and refer to not only the outerskin of a subject comprising the epidermis, but also to mucosal surfacesto which a drug composition may be administered. Examples of mucosalsurfaces include the mucosal of the respiratory (including nasal andpulmonary), oral (mouth and buccal), vaginal, introital, labial, andrectal surfaces. Hence the terms “transdermal” encompasses“transmucosal” as well.

As used herein, “enhancement,” “penetration enhancement,” or “permeationenhancement,” refer to an increase in the permeability of the skin to adrug, so as to increase the rate at which the drug permeates through theskin. Thus, “permeation enhancer,” “penetration enhancer,” or simply“enhancer” refers to an agent, or mixture of agents that achieves suchpermeation enhancement. Several compounds have been investigated for useas penetration enhancers. See, for example, U.S. Pat. Nos. 5,601,839;5,006,342; 4,973,468; 4,820,720; 4,006,218; 3,551,154; and 3,472,931. Anindex of permeation enhancers is disclosed by David W. Osborne and JillJ. Henke, in their publication entitled “Skin Penetration EnhancersCited in the Technical Literature.” published in PharmaceuticalTechnology (June 1998), which is incorporated by reference herein.

As used herein, “effective amount of an enhancer refers to an amountsufficient to increase the penetration of a drug through the skin.Methods for assaying the characteristics of permeation enhancers arewell-known in the art. See, for example, Merritt et al., “DiffusionApparatus for Skin Penetration. J. of Controlled Release 61 (1984),incorporated herein by reference in its entirety. Thus, an “effectiveamount” or a “therapeutically effective amount” of a drug refers to anon-toxic, but sufficient amount of the drug, to achieve therapeuticresults in treating a condition for which the drug is known to beeffective. It is understood that various biological factors may affectthe ability of a substance to perform its intended task, and that an“effective amount” or a “therapeutically effective amount” may bedependent in some instances on such biological factors. Further, whilethe achievement of therapeutic effects may be measured by a physician orother qualified medical personnel using evaluations known in the art, itis recognized that individual variation and response to treatments maymake the achievement of therapeutic effects a somewhat subjectivedecision. Generally speaking, the determination of an effective amountis well within the ordinary skill in the art of pharmaceutical Sciencesand medicine. See, for example, Meiner and Tonascia, “Clinical Trials:Design, Conduct, and Analysis.” Monographs in Epidemiology andBiostatistics, Vol. 8 (1986), incorporated herein by reference.

A “contraceptively effective amount” refers to the minimum amount ofdrug sufficient to produce a contraceptive effect in a subject. Thedetermination of a contraceptively effective amount of a drug iswell-within the ordinary skill in the art of pharmaceutical and medicalsciences.

As used herein, “serum level” refers to the level of a drug in the bloodof a subject. A therapeutically effective serum level may vary dependingon the therapeutic benefit desired, as well as other variables such asthe subject's age, weight, metabolism, physiological conditions such asgastrointestinal motility, renal clearance, etc. Therapeuticallyeffective serum levels may be achieved in one or more administrations,applications or dosages. As used herein, “serum level” is usedinterchangeably with terms such as blood concentration, plasma level,plasma concentration, blood level, serum concentration, serum bloodlevel, serum blood concentration, etc.

As used herein, “pharmaceutically acceptable carrier,” and “carrier” maybe used interchangeably, and refer to any inert and pharmaceuticallyacceptable material that has substantially no biological activity, andmakes up a substantial part of the formulation. The carrier may bepolymeric, such as an adhesive, or non-polymeric and is generallyadmixed with other components of the composition (e.g., drug, binders,fillers, penetration enhancers, anti-irritants, emollients, lubricants,etc., as needed) to comprise the formulation.

The term “admixed” means that a drug and/or enhancer can be dissolved,dispersed, suspended, or otherwise combined with a carrier.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary.

Concentrations, amounts, and other numerical data may be expressed orpresented herein in a range format. It is to be understood that such arange format is used merely for convenience and brevity and thus shouldbe interpreted flexibly to include not only the numerical valuesexplicitly recited as the limits of the range, but also to include allthe individual numerical values or sub-ranges encompassed within thatrange as if each numerical value and sub-range is explicitly recited. Asan illustration, a numerical range of “about 1 micron to about 5microns” should be interpreted to include not only the explicitlyrecited values of about 1 micron to about 5 microns, but also includeindividual values and sub-ranges within the indicated range. Thus,included in this numerical range are individual values such as 2, 3, and4 and sub-ranges such as from 1-3, from 2-4, and from 3-5, etc.

This same principle applies to ranges reciting only one numerical value.Furthermore, such an interpretation should apply regardless of thebreadth of the range or the characteristics being described.

B. The Invention

The present invention involves methods and formulations for effectingprogestin-only contraception in a woman in a manner that reduces orminimizes various adverse side effects known as problematic toprogestin-only contraception and further increases the convenience ofthe contraceptive regimen and decreases the risk of pregnancy throughdosing non-compliance. Specifically, the Applicants have discovered asurprising relationship between contraceptive effectiveness, sideeffects, and the dosage form of the progestin formulation. They havefound that when serum levels sufficient to provide a contraceptiveeffect are obtained by transdermal administration of a progestin thatvarious adverse side effects such as breakthrough bleeding areminimized, especially as compared to an equivalent amount of the sameprogestin administered orally. Further, Applicants have discovered thattransdermal administration of progestins for contraceptive purposesvirtually eliminates the risk of day-to-day dosing non-compliance, whichis significant with oral progestin-only contraception as each pill mustbe taken at the same time each day.

In practice, transdermal progestin administration is able to provide aminimum drug serum level and reduce or avoid serum concentration “peaks”or “spikes” typically associated with oral progestin therapies. It isbelieved that peaks may significantly contribute to the incidence ofside effects such as break through bleeding, and that by avoiding thesepeaks through the transdermal administration of a progestin, sideeffects may be minimized. Additionally, unlike oral therapies, peak drugserum levels can be reduced while minimum drug serum levels aremaintained above a threshold level in order to ensure a contraceptiveeffect in the subject. A similar reduction in peak drug serum levels inoral therapies typically also facilitates a concomitant reduction inminimum drug serum levels thus posing a risk of noneffectiveness.

Accordingly, various transdermal formulations and compositions thatcontain a contraceptively effective amount of a progestin to beadministered to a woman as part of a progestin-only contraceptiveregimen are disclosed and described herein. Various progestin-onlyformulations and articles of manufacture, including kits containingsuch, are thus contemplated, and are considered to be within the scopeof the present invention. Furthermore, methods of minimizing adverseside effects known to be associated with progestin-only contraception byutilizing such formulations are also disclosed and described. Suchadverse side effects include, without limitation, strokes, myocardialinfarctions, embolisms, breakthrough bleeding, and combinations thereof.

A wide variety of contraceptively effective progestins known to those ofordinary skill in the art can be utilized as the contraceptively activeagent in the transdermal formulations of the present invention. Examplesof such progestins can include, without limitation, progesterone,hydroxyprogesterone, megestrol acetate, dimethisterone, norgestrel,levonorgestrel, medroxyprogesterone acetate, desogestrel, norgestimate,ethynodiol diacetate, norethindrone, norethindrone acetate,norethynodrel and derivatives thereof. In one aspect, the progestin isprogesterone. In another aspect, the progestin is norethindrone. Inanother aspect, the progestin is norethindrone acetate. In yet anotheraspect, the progestin is norethynodrel. As the formulation is forprogestin-only contraception, other non-progestin type steroids oractive agents that contribute to contraception will generally not beincluded with the selected progestin in the transdermal formulation.Further, most often only a single progestin will be used in theformulation. However, in some circumstances two or more progestins,especially progestins of different type, may be combined in order toachieve a specific formulation.

The amount of progestin to be administered may be measured according toseveral different parameters. In one aspect, the rate or amount ofprogestin administered may be a rate or an amount sufficient to achievea contraceptive effect. The amount required to obtain a contraceptiveeffect may vary depending on a number of factors, including the activityor potency of the specific progestin selected, as well as physiologicalvariations among women as to drug tolerance and general metabolicissues. In one aspect, ovulation, or a lack thereof, can provide somemeasure of contraceptive effectiveness. In some cases, serum levels ofprogesterone ≤3.0 ng/ml are considered to indicate a lack of ovulation.It should be noted, however, that ovulation is highly variable amongdifferent subjects, and as such, the ≤3.0 ng/ml level may not beindicative of ovulation in all women. It has been demonstrated thatprogestins are contraceptively effective even though a large proportionof women ovulate while taking them. In another aspects, inter alfa,thickening of the cervical mucus, suppression of lutenizing hormone (LH)and follicle stimulating hormone (FSH) peaks, reduction of ciliaryactivity in the fallopian tubes, and certain alterations of theendometrium may also be indicators of contraceptive effectiveness. Assuch, it is well within the knowledge of those skilled in the art todetermine contraceptive effectiveness. In one aspect, at least about0.35 mg/day of a progestin such as norethindrone or norethindroneacetate can be administered to achieve contraceptive effectiveness. Inanother aspect, at least about 0.30 mg/day can be administered. In yetanother aspect, at least about 0.25 mg/day can be administered. In yetanother aspect, from about 0.25 mg/day to about 4.0 mg/day can beadministered.

The rate or amount of a progestin to be delivered can also be measuredaccording to serum levels. In one embodiment, the progestin may beeither norethindrone or norethindrone acetate administered at a rate andan amount that provides a minimum norethindrone serum level that issufficient to cause and sustain physiologic events in the womanresulting in contraception, while at the same time providing a maximumnorethindrone serum level that avoids a significant incidence of adverseside effects. Various maximum norethindrone serum levels arecontemplated that may avoid such adverse side effects. In one aspect,the maximum norethindrone serum level may be less than about 2400 pg/ml.In another aspect, the maximum norethindrone serum level may be fromabout 240 pg/ml to about 1920 pg/ml. In yet another aspect, the maximumnorethindrone serum level may be from about 300 pg/ml to about 1200pg/ml. In a further aspect, the maximum norethindrone serum level can befrom about 400 pg/ml to about 1100 pg/ml. Additionally, various minimumnorethindrone serum levels are contemplated that may be sufficient tocause and sustain physiologic events in the woman resulting incontraception. In one aspect, the minimum norethindrone serum level canbe at least about 160 pg/ml. In another aspect, the minimumnorethindrone serum level can be at least about 300 pg/ml. In yetanother aspect, the minimum norethindrone serum level can be at leastabout 350 pg/ml.

Serum levels can also be expressed in terms of a relationship betweenthe maximum and minimum values. For example, in one aspect the maximumnorethindrone serum level that may be up to about 15 times greater thanthe minimum norethindrone serum level. In another aspect, the maximumnorethindrone serum level may be up to about 8 times greater than theminimum norethindrone serum level. In yet another aspect, the maximumnorethindrone serum level may be up to about 4 times greater than theminimum norethindrone serum level. In a further aspect, the maximumnorethindrone serum level may be up to about 2.75 times greater than theminimum norethindrone serum level.

Contraceptive physiologic events can be sustained for varying amounts oftime following progestin administration, depending on the dosage form,the nature of any penetration enhancer present, the amount of progestinin the formulation, etc. In one aspect, physiologic events may besustained for a period of up to at least 168 hours. In another aspect,physiologic events associated with contraception may be sustained for aperiod from about 24 hours to about 168 hours. In yet another aspect,contraception may be sustained for a period of from about 24 hours toabout 96 hours. In a further aspect, contraception may be sustained fora period of from about 48 hours to about 168 hours.

In accordance with another aspect of the invention, other progestins maybe administered according to their additional potencies in amounts thatare sufficient to provide a therapeutic effect equivalent to that ofnorethindrone. Those of ordinary skill in the art will readily recognizea number of mechanisms for determining the correct amount of a givenprogestin to substantially match the potency of a specific amount ofnorethindrone.

The exact amount of progestin to be included in the transdermalformulations of the present invention to achieve a contraceptivelyeffective amount is also considered to be within the knowledge of thoseskilled in the art. Such a determination may depend again on theactivity or potency of the specific progestin selected and physiologicalvariations among women as to drug tolerance and general metabolicissues. Further, considerations for drug load may also be made in viewof specifically desired properties for the transdermal formulation, suchas size, delivery rate, and duration of administration, and may rangefrom subsaturated to supersaturated concentrations. However, in oneaspect, the amount of progestin may be from about 0.01% w/w to about 50%w/w of the formulation. In a further aspect, the amount of progestin maybe from about 0.3% w/w to about 30% w/w of the formulation. In anotheraspect, the amount of progestin may be from about 1% w/w to about 15%w/w. In yet another aspect, the amount of progestin may be from about2.5% w/w to about 12% w/w. In a further aspect, the amount of progestinmay be about 5% w/w to about 10% w/w of the formulation. In anadditional aspect, the progestin amount may be about 10% w/w of theformulation.

A number of pharmaceutically acceptable transdermal formulations andmethods for administering progestin may be used for achieving thedesired aspects of the present invention. The transdermal drug deliverysystem for the progestin may take a variety of well-known deliveryformulations, including but not limited to transdermal patches such asadhesive matrix patches, liquid reservoir system (LRS) patches,transmucosal patches or tablets, and topical formulations, such ascreams, lotions, ointments, gels, pastes, mousses, aerosols, sprays,suppositories, etc. In one general aspect, the transdermal drug deliverysystem can comprise a pharmaceutically acceptable carrier and aprogestin for transdermal delivery.

When presented in the form of a transdermal patch, the transdermal drugdelivery system of the present invention may include structuralcomponents, as known in the art. For example, in the case of an adhesivematrix patch, a distal backing can be laminated to a polymer layer. Sucha distal backing defines the side of the matrix patch that faces theenvironment, i.e., distal to the skin or mucosa. The backing layerfunctions to protect the matrix polymer layer and the transdermalformulation, and to provide a layer that prevents loss of progestin tothe environment. Thus, the material chosen for the backing should becompatible with the polymer layer, progestin, and any optionalingredient such as an enhancer, and should be minimally permeable to anycomponents of the matrix patch. In one aspect, the backing can be opaqueto protect components of the matrix patch from degradation from exposureto ultraviolet light. In another aspect, the backing can be transparent.Furthermore, the backing should be capable of binding to and supportingthe polymer layer, yet should be pliable enough to accommodate themovements of a person using the matrix patch.

Suitable materials for the backing include, but are not limited to:metal foils, metalized polyfoils, composite foils or films containingpolyester such as polyester terephthalate, polyester or aluminizedpolyester, polytetrafluoroethylene, polyether block amide copolymers,polyethylene methyl methacrylate block copolymers, polyurethanes,polyvinylidene chloride, nylon, silicone elastomers, rubber basedpolyisobutylene, styrene, styrene-butadiene and styrene-isoprenecopolymers, polyethylene, and polypropylene. Additionally, the backingmay include various foams, such as closed cell foams. Examples mayinclude, without limitation, polyolefin foams, polyvinyl chloride foams,poly urethane foams, polyethylene foams, etc. In one aspect of theinvention, the backing layer may have a thickness of about 0.0005 to 0.1inch.

Further, a release liner may be temporarily provided upon the proximalside (side to adhere to the skin) of the adhesive layer. Such a linerprovides many of the same functions as the backing layer, prior toadhesion of the patch to the skin. In use, the release liner is peeledfrom the adhesive layer just prior to application and discarded. Therelease liner can be made of the same materials as the backing layer, orother suitable films coated with an appropriate release surface.

In addition to containing the progestin, transdermal formulations of thepresent invention may also include one or more of a number of otheradditives, such as diluents, excipients, emollients, plasticizers, skinirritation reducing agents, or a mixture thereof. Such materials arepharmaceutically acceptable in that they are nontoxic, do not hinderdrug delivery, and are not for any other reasons biologically orotherwise undesirable. Examples of such additional materials includewater, mineral oils, silicone, inorganic gels, aqueous emulsions, liquidsugars, waxes, petroleum jellies, plasticizers, low molecular weightpolymers, and a variety of other oils and polymeric materials. Thesetypes of components, as well as others not specifically recited, arewell known in the art for inclusion in various transdermal formulations,and may be added as desired to the transdermal drug delivery system ofthe present invention in specific types and amounts in order to achievea desired result. Additionally, many transdermal drug deliveryformulations have a tendency to cause skin irritation after prolongedexposure to the skin, thus addition of a skin irritation reducing agentaids in achieving a composition that is better tolerated by the skin. Inone aspect, the skin irritation reducing agent may be glycerin, asdisclosed in U.S. Pat. No. 4,855,294, which is incorporated by referencein its entirety.

As described herein, the transdermal formulations of the presentinvention may also optionally include a permeation enhancer, or mixtureof permeation enhancers. Useful permeation enhancers may include,without limitation, fatty acids, fatty acid esters, fatty alcohols,fatty acid esters of lactic acid or glycolic acid, glycerol tri-, di-,and monoesters, triacetin, short chain alcohols, and mixtures thereof.Specific species or combinations or species may be selected from theabove listed classes of compounds by one skilled in the art, in order tooptimize enhancement of the particular progestin employed. As more fullyenumerated below, it has been found that sorbitan ester-type,lauryl-type, and polyol-type agents provide a significant penetrationenhancing effect on norethindrone and norethindrone acetate. One skilledin the art would, however, understand that many other enhancers could beutilized in these formulations, and would thus be included within thescope of the present invention.

In one aspect of the present invention, the permeation enhancer is asorbitan ester-type enhancer. Sorbitan ester-type enhancers arediscussed in U.S. Pat. Nos. 5,227,169 and 5,212,199, which areincorporated by reference in their entireties. Exemplary sorbitan esterscan be, without limitation, longchain sorbitan monoesters such assorbitan monooleate and sorbitan monolaurate.

In another aspect, the permeation enhancer included in the transdermalformulation may be a lauryl-type enhancer. A variety of lauryl-typeenhancers may be suitable for use in the present invention. However, inone aspect the lauryl-type enhancer used may include without limitation,lauryl alcohol, 1-lauryl-2-pyrrolidone, and mixtures thereof. In anotheraspect, the enhancer may be a mixture of lauryl alcohol in an amount ofabout 5% w/w and 1-lauryl-2-pyrrolidone in an amount of about 3% w/w. Inyet another aspect, the permeation enhancer may be a polyol-typeenhancer. Further, a variety of polyol-type enhancers may be suitablefor use in the present invention. However, in one aspect, thepolyol-type enhancer used may be dipropylene glycol.

The specific sorbitan ester-, lauryl-, or polyol-type enhancer, and theamount thereof, may be selected by one of ordinary skill in the artdepending on a specific result to be achieved. However, as a generalmatter, the amount of enhancer included in the transdermal formulationmay be from about 0.01% w/w to about 50% w/w of the formulation. In amore detailed aspect, the amount of enhancer may be from about 3% w/w toabout 15% w/w of the formulation. In a further aspect, the amount ofenhancer may be about 10% w/w of the formulation. In an additionalaspect, the amount of enhancer may be about 5% w/w of the formulation.

In yet another aspect, the permeation enhancer in the transdermalformulation may be isopropyl myristate (IPM). IPM can be included as thesole enhancer, or the transdermal formulation can include IPM and atleast one other enhancer, such as, without limitation, lauryl alcohol,sorbitan monooleate, or dipropylene glycol. In one particular aspect ofthe invention, the enhancer may be a combination of lauryl alcohol andisopropyl myristate. A more detailed discussion of permeation enhancercombinations of lauryl alcohol and isopropyl myristate can be found inApplicant's copending U.S. Patent Application No. 60/705,289 filed onAug. 3, 2005 entitled “Formulations and Methods for Enhancing theTransdermal Penetration of a Drug,” which is incorporated herein byreference.

In one general aspect, the transdermal drug delivery system of thepresent invention can comprise a pharmaceutically acceptable carrierintended to contain the progestin and other optional components. Anumber of pharmaceutically acceptable carriers are known to those ofordinary skill in the art and may be used in connection with the presentinvention.

The pharmaceutically acceptable carrier of an LRS patch may be of anysuitable viscous material known to those skilled in the art oftransdermal drug delivery. Such carriers are typically a fluid ofdesired viscosity, such as a gel or ointment, which is formulated forconfinement in a reservoir having an impermeable backing and a skincontacting permeable membrane, or membrane adhesive laminate providingdiffusional contact between the reservoir contents and the skin. Such aviscous carrier may contain both the progestin to be transdermallydelivered as well as other optional components of the transdermalformulation. LRS patches are those described or referred to in U.S. Pat.Nos. 4,849,224, and 4,983,395, which are hereby incorporated byreference in their entirety.

The present invention contemplates various structural types oftransdermal matrix patches. For example, monolithic systems where theprogestin is contained directly in a single pressure sensitive adhesivelayer, as well as systems containing one or more polymeric reservoirs inaddition to the pressure sensitive adhesive layer may be utilized. Inaspects comprising systems having multiple layers/laminates, a ratecontrolling member may be included. Generally, a rate controlling memberis located between a reservoir layer and the skin. In those aspectsincluding a delivery layer and a reservoir layer, the rate controllingmember may be adhered between a proximal side of the reservoir layer,and a distal side of the delivery layer. The rate controlling member isprovided for the purpose of metering, or controlling, the rate at whichdrug and/or permeation enhancer migrates from the storage layer into thedelivery layer. As noted herein, in one aspect of the present invention,a permeation enhancer may be used to increase the delivery rate of thedrug, and thus may also be used to vary other parameters, such as patchsize, etc.

In one aspect, the pressure-sensitive adhesive of the pharmaceuticallyacceptable carrier can be suitable for long-term (e.g., greater than 1day, may be about 3-4 days, or longer such as 1-4 weeks) contact withthe skin. In another aspect, the pressure-sensitive adhesive of thecarrier is suitable for a short-term administration (e.g., for a fewminutes to a few hours, less than or equal to 1 day). Such adhesivesmust be physically and chemically compatible with the progestin and anyoptional enhancer present, and with any carriers and/or vehicles orother additives incorporated into the formulation. In one aspect of theinvention, the adhesives of the pharmaceutically acceptable carrier caninclude polymeric adhesives. Example of such adhesives can includewithout limitation, acrylic adhesives including cross-linked anduncross-linked acrylic copolymers; vinyl acetate adhesives; natural andsynthetic rubbers including polyisobutylenes, neoprenes, polybutadienes,and polyisoprenes; ethylenevinylacetate copolymers; polysiloxanes;polyacrylates; polyurethanes; plasticized weight polyether block amidecopolymers, and plasticized styrene-rubber block copolymers or mixturesthereof. In yet another aspect of the invention, contact adhesives foruse in the pharmaceutically acceptable carrier layer are acrylicadhesives, such as DUROTAK™ 87-2888 adhesive (National Starch & ChemicalCo., Bridgewater, N.J.); and polyisobutylene adhesives such as ARCARE®MA-24 (Adhesives Research, Glen Rock, Pa.) and ethylene vinyl acetatecopolymer adhesives. Those of ordinary skill in the art will appreciatethat the specific type and amount of adhesive polymer used may beselected depending upon the desired specific characteristics of thefinal product. However, in one aspect, the amount of adhesive polymer inthe adhesive matrix layer may be at least about 50% w/w of the adhesivelayer. In another aspect, the amount may be at least about 60% w/w ofthe adhesive layer. In yet another aspect, the amount may be at leastabout 85% w/w of the adhesive layer. In a further aspect, the amount maybe at least about 90% w/w of the adhesive layer. In an additionalaspect, the amount may be from about 50% w/w to about 95% w/w of theadhesive layer.

In one aspect of the present invention, the carrier can be abiocompatible polymer. In another aspect, the carrier is an adhesivesuch as a polymeric adhesive matrix. In yet another aspect, thepolymeric adhesive may be an acrylic polymer, such as an acrylicpressure sensitive adhesive. The carrier, in some aspects, may containboth the progestin to be transdermally delivered, and a permeationenhancer or other optional components.

The transdermal formulations of the present invention can also beprovided with pharmaceutical carriers that improve the stability ofprogestins during long-term storage. Such compositions may compriseethylhexylacrylate polymers, or other carriers that do not contain orform acid functional groups upon storage, as described in U.S. Pat. No.5,780,050, which is incorporated by reference herein. Methods forproviding such hormones to females, as well as males, are also wellknown. See, U.S. Pat. Nos. 5,460,820, 5,152,997, and 5,783,208, whichare incorporated by reference herein. It is appreciated that using thedisclosure of the present invention, one skilled in the art can readilyaccomplish the objective of the above-referenced patents.

The formulations of the present invention can include sustained releaseformulations that administer therapeutically effective amounts of aprogestin over an extended period of time. However, in one aspect, thesustained delivery period of the progestin may be for at least about 7days. In another aspect, the sustained delivery period may be at leastabout 5 days. In a further aspect, the sustained delivery period may beat least about 3 days. In yet another aspect, the period may be about 24hours.

In addition to the methods of providing progestin only contraception tominimize breakthrough bleeding side effects associated withprogestin-only contraception, the present invention includes a kit forproviding the progestin only contraception according to the methodsdisclosed herein. The kit can comprise a transdermally administrableformulation having a contraceptively effective amount of a singleprogestin as the sole active hormonal agent, and instructions describinga method of using the transdermally administrable formulation. Thetransdermal formulation can utilize the progestins, optional enhancers,dosage forms, and other transdermal components described herein.

EXAMPLES

The following examples of progestin-only contraceptive formulations areprovided to promote a more clear understanding of certain embodiments ofthe present invention, and are in no way meant as a limitation thereon.

Example 1

Transdermal matrix systems containing norethindrone acetate can be madeas follows. The solids contents of an acrylic adhesive solution,(DUROTAK™ 87-2888, National Starch) are determined by placing Smallamounts into pre weighed aluminum dishes which are then put in aconvection oven (Model A4718-Q, Blue M) at 75° C. overnight. Followingevaporation of the solvents, the weight of the dry adhesive is obtainedand the solids content calculated as a ratio of the dry to wet weight.The adhesive 87-2888 contains approximately 32-35% solids and is usedundiluted. Known quantities of the adhesive are weighed into glassbottles based on previously determined solids content. An appropriatequantity of norethindrone acetate (NEA) is added to the liquid adhesivein each bottle to give about a 5% w/w NEA concentration upon drying. Thebottles are capped and sealed with parafilm and rotated until all theNEA is dissolved. An appropriate amount of sorbitan monooleate (SMO)enhancer is added to the bottles containing the NEA in adhesive to givethe desired compositions having about 10% w/w SMO enhancer upon drying.Each bottle is again tightly capped, sealed with parafilm and rotatedovernight during which time the NEA and the enhancer dissolve to yield aclear solution.

An appropriate amount of the composition (about 10 g) is then placedonto the high release side of a silicone release-coated 3 Mil thickpolyester (PET) liner (Loparex Inc., 10393S) and manually cast with a 10Mil gap casting knife. Each cast is placed in a convection oven (ModelA4718-Q, Blue M) at 75° C. for 15 minutes. After drying, each cast isthen laminated with a 3 Mil polyethylene (PET) monolayer backing film(3M™, COTRAN™ 9720). The cast and backing film can then be cut toprovide a proper delivery dosage, namely 22 cm² for 0.2 mg/day and 33cm² for 0.3 mg/day patches.

Example 2

Transdermal matrix systems containing norethindrone acetate can also bemade as follows. The solids contents of an acrylic adhesive solution,(DUROTAK™ 87-900A) are determined by placing small amounts intopre-weighed aluminum dishes which are then put in a convection oven(Model A4718-Q, Blue M) at 75° C. overnight. Following evaporation ofthe solvents, the weight of the dry adhesive is obtained and the Solidscontent calculated as a ratio of the dry to wet weight.

The adhesive 87-900A contains approximately 40-44% solids and is usedundiluted. Lauryl alcohol is a solid at room temperature and has to bemelted by heating a small quantity held in a glass jar in a water bathprior to use. For each casting solution being prepared, the appropriateamount of soluble polyvinylpyrrolidone (PVP) K-12 to yield 10% w/w inthe dried film is weighed directly into a jar and the minimum amount ofabsolute ethanol calculated to completely dissolve the PVP is added tothe jar. After dissolving the PVP based on the previously determinedsolids content, a known volume of the adhesive is weighed into the jarand, appropriate amounts of Norethindrone acetate (NEA), lauryl alcohol(LA), isopropyl myristate (IPM) (with the appropriate overages) areadded to provide the desired compositions upon drying 10% w/w NEA, 5%w/w LA, 5% w/w IPM and 10% w/w PVP-K12. The bottles are tightly capped,sealed with parafilm and rotated over night during which time all theingredients dissolve to yield a translucent solution.

A small amount of the formulation (about 10 g) is placed onto afluoropolymer coated 3 Mil thick polyester (PET) liner (3M™, SCOTCHPAK™,1022) and manually cast with a 10 mil gap casting knife. The cast isplaced in a convection oven (Model A4718-Q, Blue M) at 75° C. for 15minutes. After drying, the cast is laminated with the polyester side ofa 2 Mil (PET/EVA) laminate backing film (3M™, SCOTCHPAK™, 9739). Thecast and backing film can then be cut to appropriate sizes to provide aproper delivery dosage, 0.2 mg/day and 0.3 mg/day patches.

Example 3

A clinical trial using the transdermal formulation of Example 1 wasconducted for the purposes of comparing such formulations with oralprogestin-only contraceptive tablets (NOR QD®, Watson Pharmaceuticals,Inc.) Volunteer subjects were subjected to a screening and baselineperiod consisting of a 4-week washout of previous contraceptivetreatment, if necessary, followed by approximately a one month baselineevaluation period (cycle 1) which consisted of one full menses cycle todetermine eligibility for participating in the study. Eligibility wasbased on whether a subject ovulated (serum progesterone >3 ng/ml) andhad a favorable cervical mucus score (10) during cycle 1. Subjects whoqualified for entry into the study were randomized into two 12-weekstudy groups:

-   -   once weekly application to the abdomen of 0.3 mg/day formulation        of Example 1 for 12 consecutive weeks starting on the first day        of bleeding of the first menstrual cycle following        randomization; and    -   once daily oral administration of 0.35 mg NOR QD®        (norethindrone-only formulation) for 12 consecutive weeks        starting on the first day of bleeding of the first menstrual        cycle following randomization.

A third study group was also established, the results of which are notincluded herein. A treatment period consisted of 12-week study dividedinto three cycles, namely cycles 2-4. Each cycle was approximately 4weeks in duration, beginning on the first day of menstrual bleeding fora give cycle.

Example 4

Plasma norethindrone (NE) concentration measurements were performed onthe study groups of Example 3 to determine the peak and trough levels ofNE during the third month of treatment, Cycle 4. For the oral 0.35 mgNOR QD® group, trough NE plasma concentration levels were collectedprior to the Subjects taking their morning dose, and peak NE plasmaconcentration levels were collected one hour following dosing. For the0.3 mg/day NOR TD™ group, peak and trough NE plasma concentration valueswere determined by comparing the date/time of the concentration to thedate/time of the last transdermal patch application. For example, bloodNE samples were considered peak concentration levels if the blood wascollected >24 hours and <96 hours from the time of the last transdermalpatch application. If however, the difference between when the blood NEsample was collected and the time of the last transdermal patchapplication was <24 hours or was between 96 and 168 hours, theconcentration level was considered trough. Plasma NE concentrations aresummarized for each treatment group in Table 1.

TABLE 1 Plasma NE concentrations summarized for each treatment groupPlasma NE concentrations (pg/mL) 0.3 mg/day 0.35 mg NOR TD ™* NOR QD ®**Peak 549.8 2721.9 Trough 367.6 551.2 *80 subjects **79 subjects

The mean peak NE levels for the 0.3 mg/day NOR TD™ dose group is similarto levels (600 pg/mL) that are thought to be required to consistentlyinhibit ovulation when using subdermal implants of NEA. As can be seenin Table 1, daily ingestion of an oral NE formulation producessignificantly higher plasma NE concentrations than the transdermal NEformulation. Moreover, the difference between peak and trough associatedwith the transdermal formulation is much less than the differenceassociated with the oral formulation.

Example 5

The portion of each group that did not ovulate was during the treatmentis shown in Table 2. A direct quantitative assessment was obtained bymeasuring serum progesterone levels. Non-ovulation was defined as serumprogesterone levels of ≤3 ng/mL.

TABLE 2 The proportion of subjects who did not ovulate Ovulation 0.3mg/day 0.35 mg NOR TD ™* NOR QD ®** Ovulated 55% 49% Did not ovulate 45%51% *80 subjects **79 subjects

The 95% confidence interval lower limit for the 0.3 mg/day NOR TD™treatment group was -18.6%, and is therefore within a 20% equivalencebound indicating that the two treatment groups are consideredequivalent.

Example 6

Cervical mucus samples were collected between Days 11 and 17 of Cycle 4and scored according to WHO Laboratory Manual for the Examination ofHuman Semen and Sperm-Cervical Mucus Interaction, (4^(th) ed., CambridgeUniversity Press, 1999), which is incorporated herein by reference.Variables evaluated included volume, spinnbarkeit, consistency,cellularity, and ferning. The scale for each variable ranged from 0 to3, allowing a maximum total score of 15. The score for each variable wastotaled to produce the cervical mucus score, which could range from 0 to15. Using the scoring system from the WHO lab manual, a score ≥10 wasused to indicate cervical mucus conditions favorable for spermpenetration and a score <10 was used to indicate unfavorable mucusconditions for sperm penetration. The results of this evaluation areshown in Table 3.

TABLE 3 A comparison of cervical mucus status Cervical Mucus Status(Cycle 4) 0.3 mg/day 0.35 mg NOR TD ™* NOR QD ®** % Favorable 11% 8% %Unfavorable 89% 92% *80 subjects **79 subjects

The 95% confidence interval lower limit for the 0.3 mg/day NOR TD™treatment group was −12.1%, and is therefore within a 20% equivalencebound indicating that the two treatment groups are consideredequivalent.

Example 7

Subjects in the treatment groups of Example 3 were evaluated for anybreakthrough bleeding that occurred during the three cycles. A number ofsubjects were included in this evaluation that were disqualified priorto the evaluations in Examples 4-6. Breakthrough bleeding orintermenstrual bleeding was defined as any bleeding or spottingoccurring during the menstrual cycle, excluding contiguous bleeding withmenses. Breakthrough bleeding was categorized using the followingcriteria:

-   -   none    -   spotting (≤1 sanitary pad/tampon used)    -   bleeding (≥2 sanitary pad/tampons used)

Results from the breakthrough bleeding studies are contained in Tables 4and 5.

TABLE 4 A comparison of the percentage of women that experiencedbreakthrough bleeding (spotting) Breakthrough Bleeding: Spotting Cycle 2Cycle 3 Cycle 4 0.3 mg/day 13.6% 17.8% 18.4% NOR TD ™* 0.35 mg 17.9%18.4% 21.9% NOR QD ®** *112 subjects **113 subjects

TABLE 5 A comparison of the percentage of women that experiencedbreakthrough bleeding (bleeding) Breakthrough Bleeding: Spotting Cycle 2Cycle 3 Cycle 4 0.3 mg/day 20.0% 23.4% 20.4% NOR TD ™* 0.35 mg 14.3%27.2% 34.4% NOR QD ®** *112 subjects **113 subjects

As can be seen from these data, the incidence of breakthrough bleedingwas lower in the 0.3 mg/day NOR TD™ group than the oral 0.35 mg NOR QD®group, particularly for bleeding during cycle 4.

Examples 5 and 6 demonstrate that the 0.3 mg/day NOR TD™ and the 0.35 mgNOR QD® formulations may be therapeutically equivalent because theyappear to provide equivalent levels of contraceptive protection asdemonstrated by the similarities observed in the study populationsregarding ovulation and cervical mucus status.

Given this apparent dose equivalence and similar contraceptive effectbetween the 0.30 mg/day transdermal and the 0.35 mg oral formulations, asurprising relationship appears between the progestin dosage form andthe incidence of breakthrough bleeding in the study populations shown inExample 7. Specifically, transdermal delivery of the NEA-onlyformulation caused overall fewer incidents of breakthrough bleeding thanthe oral NE-only formulation. It is possible that the higher incidenceof breakthrough bleeding in the group taking the 0.35 mg NOR QD® oralformulation may be a result of the significantly higher peak NE serumlevels observed as compared to the 0.3 mg/day NOR TD™ transdermalformulation, as shown in Example 4. Thus the higher peak serum level ofNE as a result of taking an oral NE formulation may be associated withthe higher incidence of side effects. Moreover, as shown in Table 1, thedifference between peak and trough associated with the transdermalformulation is much less than the difference associated with the oralformulation. As such, NE serum level rise and fall rapidly throughout a24 hour period. This rapid change may also account for the differencesin breakthrough bleeding side effects observed between the oral andtransdermal formulations.

Regardless of the method of action, however, it is apparent from thesedata that the transdermal NEA-only formulation is superior to the oralNE-only formulation because, while both attain substantially similarcontraceptive effects, the transdermal formulation further minimizesside effects such as breakthrough bleeding and reduce the risk of dosagenon-compliance, and therefore increases the overall efficacy of thecontraceptive regimen.

It is to be understood that the above-described compositions and modesof application are only illustrative of preferred embodiments of thepresent invention.

Numerous modifications and alternative arrangements may be devised bythose skilled in the art without departing from the spirit and scope ofthe present invention and the appended claims are intended to cover suchmodifications and arrangements.

Thus, while the present invention has been described above withparticularity and detail in connection with what is presently deemed tobe the most practical and preferred embodiments of the invention, itwill be apparent to those of ordinary skill in the art that numerousmodifications, including, but not limited to, variations in size,materials, shape, form, function and manner of operation, assembly anduse may be made without departing from the principles and concepts setforth herein.

What is claimed is:
 1. A transdermal patch comprising: a) norethindroneas the sole hormonal active agent or a combination of norethindrone andnorethindrone acetate as the sole hormonal active agents in an amount offrom 1% to 15% w/w; and b) a permeation enhancer comprising (i)isopropyl myristate and (ii) lauryl alcohol, wherein the transdermalpatch is formulated to minimize adverse side effects associated withprogestin-only contraception by providing: a) a minimum norethindroneserum level of at least 300 pg/ml from 24 hours to 168 hours followingapplication of the patch to an outer skin surface; and b) a maximumnorethindrone serum level of less than 2400 pg/ml from about 24 to 96hours following application of the patch to the outer skin surface,wherein the side effects are selected from the group consisting ofstrokes, myocardial infarctions, embolisms, breakthrough bleeding andcombinations thereof.
 2. The transdermal patch of claim 1 wherein thepermeation enhancer is present in an amount of from 0.01% to 50% w/w. 3.The transdermal patch of claim 2 wherein the permeation enhancer ispresent in an amount of from 3% to 15% w/w.
 4. The transdermal patch ofclaim 1, wherein the sole hormonal active agents are present in anamount of from 2.5% to 12% w/w.
 5. The transdermal patch of claim 4,wherein the sole hormonal active agents are present in an amount of from5% to 10% w/w.
 6. The transdermal patch of claim 1, wherein the solehormonal active agents are present in an amount of 10% w/w.
 7. Thetransdermal patch of claim 1, wherein the permeation enhancer is presentin an amount of 5% w/w.
 8. The transdermal patch of claim 1, wherein thepermeation enhancer is present in an amount of 10% w/w.
 9. Thetransdermal patch of claim 1, wherein the sole active hormonal agent isnorethindrone.
 10. The transdermal patch of claim 1, wherein the soleactive hormonal agent is a combination of norethindrone andnorethindrone acetate.
 11. The transdermal patch of claim 1, wherein thetransdermal patch is formulated to deliver the sole active hormonalagent in an amount of 0.2 mg/day.
 12. The transdermal patch of claim 1,wherein the transdermal patch is formulated to deliver the sole activehormonal agent in an amount of 0.25 mg/day.
 13. The transdermal patch ofclaim 1, wherein the transdermal patch is formulated to deliver the soleactive hormonal agent in an amount of 0.3 mg/day.
 14. The transdermalpatch of claim 1, wherein the transdermal patch is formulated to deliverthe sole active hormonal agent in an amount of 0.35 mg/day.
 15. Thetransdermal patch of claim 1, wherein the transdermal patch is a matrixpatch.
 16. The transdermal patch of claim 15, wherein the matrix patchcomprises an acrylic polymer adhesive.
 17. The transdermal patch ofclaim 1, wherein the transdermal patch is a transdermal liquid systempatch.
 18. The transdermal patch of claim 1, wherein the transdermalpatch further comprises diluents, emollients, plasticizers, skinirritation reducing agents, or a mixture thereof.
 19. The transdermalpatch of claim 18, wherein the transdermal patch includes a skinirritation reducing agent and wherein the skin irritation reducing agentis glycerin.
 20. The transdermal patch of claim 1, wherein the soleactive hormonal agent is a combination of norethindrone andnorethindrone acetate, which are present in an amount of from 2.5% to12% w/w; the permeation enhancer is present an amount of from 3% to 15%w/w; and the patch further comprises a diluent, an emollient, aplasticizer, a skin irritation reducing agent, or a mixture thereof. 21.The transdermal patch of claim 20, wherein the patch is a matrix patchand comprises an acrylic polymer adhesive.